Much effort has hitherto been made to enhance sensitivity of silver halide photographic materials and to decrease residual colors after processing. It has been known that sensitizing dyes used for spectral sensitization greatly affect properties of the silver halide photographic materials. In the sensitizing dyes, the slight difference in structure greatly affects the photographic properties such as sensitivity, fog, storage stability and residual coloration (residual colors), and the use of two or more of the sensitizing dyes in combination also greatly affects the photographic properties. However, it is difficult to predict its effect before hand. Accordingly, many researchers have hitherto made effort to synthesize many sensitizing dyes and to study the use of many sensitizing dyes in combination, thereby examining their photographic properties. However, it is still impossible to predict the photographic properties in the present circumstances. For the above-mentioned reason, a technique for spectrally sensitizing the silver halide photographic materials at high sensitivity without adverse effects such as fog and residual colors has been desired.
When it is desired that the absorption maximum of the sensitizing dye is shifted to the long wavelength side, a naphthazole nucleus has hitherto been widely used in which a benzene ring is further condensed with a benzazole nucleus. However, a recent strong demand toward enhancement in sensitivity increases the amount of the dye added, while a reduction in a processing waste solution for complying with rapid photographic processing and environmental problems must be complied with. A highly hydrophobic dye such as the naphthazole nucleus-containing dye becomes difficult to meet such demands.
In Japanese Patent Application No. 124612/2000 (corresponding to U.S. Patent Application Publication No. 2002/0058216A1), the present inventors have disclosed that a sensitizing dye in which an azole nucleus having a specific heterocycle condensed is used in place of a naphthazole nucleus is higher in sensitivity and more decreased in residual colors than a naphthazole dye. However, such a dye is much accumulated in a processing solution after processing in principle, so that the problem has become clear that a fatigued processing solution is liable to fluctuate the photographic properties.